Mercedes-Benz OM651 2.1 and 1.8 CDI: common problems by mileage
The OM651 is the Mercedes-Benz four-cylinder diesel from 2008, mostly 2,143 cc and sold as 200 to 250 CDI (later "d"), in everything from the C- and E-Class to the Sprinter and Vito. Early versions with Delphi piezo injectors had a run of injector failures; beyond that the usual work is injector sealing, charge-air hoses and the emissions equipment.
Updated · written by ipacen from documented workshop experience
- Engine codes
- OM651 (DE22LA 2,143 cc, DE18LA 1,796 cc)
- Displacement
- 2,143 cc (sold as 2.2) and 1,796 cc
- Power
- 70–150 kW (95–204 hp)
- Built
- 2008–2019
- Timing drive
- Chain
- Fuel system
- Common rail (Delphi piezo injectors on many early engines, solenoid injectors on later ones)
Problems at a glance
| Problem | Typical mileage |
|---|---|
| Injector failure on early engines (Delphi piezo) high severity | 40,000–150,000 km 25,000–95,000 miles |
| Injector seal leaks and seized injectors medium severity | 100,000–250,000 km 60,000–155,000 miles |
| Split charge-air hoses and limp mode medium severity | 100,000–250,000 km 60,000–155,000 miles |
Injector failure on early engines (Delphi piezo)
Symptoms
- Misfire, rough running or sudden stalling
- Engine will not restart after cutting out
- Knocking, or hydraulic lock if an injector sticks open
- Injector or rail pressure fault codes
Fault codes
Why it happens
Many early engines (about 2008–2011) had Delphi direct-acting piezo injectors that could stick or leak. Mercedes-Benz ran service measures to replace them, and later engines use a different injector.
How to confirm it
- Check by VIN whether the injector service measure applies and has been done.
- Read injector quantity corrections and run a leak-off test.
- Before cranking an engine that stopped suddenly, remove the glow plugs and check for fuel in a cylinder.
The fix
Replace the injectors with the current part (as a set where the service measure applies), with new seals and clamp bolts, and code them. Check the piston and con-rod of any cylinder that hydro-locked.
Injector seal leaks and seized injectors
Symptoms
- Puffing noise and exhaust smell from the top of the engine
- Black tar around an injector
- Rough idle on one cylinder
- Smell of exhaust in the cabin
Fault codes
Usually no generic fault code: go by the symptoms and the tests below.
Why it happens
If the copper seal under an injector stops sealing, combustion gas escapes past it, leaves carbon and cements the injector into the head. Reused clamp bolts and wrong torque are the usual start.
How to confirm it
- With the engine running, check each injector with soapy water for bubbles.
- Look for carbon crust in the injector wells.
- Check the clamp bolts for correct torque.
The fix
Extract the injector (penetrating oil and a puller; worst case the head comes off), clean the bore and seat, new seal and stretch bolt, torque to specification.
Split charge-air hoses and limp mode
Symptoms
- Sudden loss of power (limp mode), often under load or on a hill
- Whoosh or whistle under boost
- Oily charge-air hoses or intercooler pipes
- Underboost fault code
Fault codes
Why it happens
Rubber charge-air hoses soften with oil vapour and heat and split; plastic pipes crack near the clamps. Hard-working vans such as the Sprinter and Vito are the most affected.
How to confirm it
- Smoke-test or pressure-test the boost side with the engine off.
- Log specified against actual boost on a road test.
- Inspect hoses at the turbo and intercooler ends with the undertray off.
The fix
Replace the split hose or cracked pipe with good-quality parts and new clamps, and clean the oil out of the intercooler.
Known-good values
Add readings from a healthy Mercedes OM651Readings from Mercedes OM651 engines that run correctly, reported by mechanics on ipacen. Each member counts once; the median shows from 3 members up, with the middle half of the readings as the range. No readings yet: be the first.
See the values you can report and the typical guide
| Value | Typical guide | Measured by members |
|---|---|---|
| Engine | ||
| Idle speed, warm (rpm) | Usually about 650–900 rpm | — |
| Coolant temperature, fully warm (°C) | About 85–105 °C | — |
| Oil pressure, hot idle (bar) | Typically above about 1.0 bar | — |
| Oil pressure, hot, 2,000 rpm (bar) | Typically above about 2.5 bar | — |
| Compression, typical cylinder (bar) | Petrol about 11–15 bar, diesel about 25–35 bar | — |
| Air and fuel | ||
| Air mass, warm idle (g/s) | Petrol: roughly 1 g/s per litre of engine size | — |
| Air mass, warm idle (as mg per stroke) (mg/stroke) | Compare with specified in live data; changes with EGR | — |
| Boost at full load (absolute) (mbar) | Turbo engines: compare with specified boost | — |
| Fuel system | ||
| Fuel pressure, low-pressure side, idle (bar) | Check the specification for the system | — |
| Rail pressure, warm idle (bar) | Diesel common rail: typically about 250–400 bar | — |
| Rail pressure while cranking (bar) | Typically past about 200–300 bar within 1–2 s | — |
| Largest injector correction, warm idle (mg/stroke) | Typically within about ±2–3 mg per stroke | — |
| Emissions | ||
| Particulate filter differential pressure, warm idle (mbar) | Low on a clean filter; compare with the reading at 2,500 rpm | — |
| Electrical | ||
| Charging voltage, 2,000 rpm (V) | About 13.8–14.7 V | — |
| Lowest battery voltage while cranking (V) | Above about 9.6 V | — |
| Crankshaft sensor resistance (inductive type) (Ω) | About 200–2,000 Ω | — |
The guide is ipacen's typical range, not manufacturer data. Member values are what colleagues measured on healthy cars; always compare with the specification for the engine.
Which cars have the Mercedes OM651
- Mercedes-Benz: C-Class (W204, W205) and E-Class (W212) 200 to 250 CDI/BlueTEC; GLK (X204); ML 250 BlueTEC (W166); A-, B-, CLA- and GLA-Class 180 to 220 CDI; SLK 250 CDI; Sprinter (906, 2009–2018); Vito and Viano (W639 from 2010, W447)
Cases with this engine
Share yoursMercedes OM651: questions and answers
What are the most common problems with the Mercedes OM651?
The most reported are injector failure on early engines (Delphi piezo); injector seal leaks and seized injectors; split charge-air hoses and limp mode. Each one is described below with its symptoms, fault codes, how to confirm it and the usual fix.
At what mileage does the Mercedes OM651 have injector failure on early engines (Delphi piezo)?
Typically between 40,000–150,000 km (25,000–95,000 miles), depending on use and maintenance. Many early engines (about 2008–2011) had Delphi direct-acting piezo injectors that could stick or leak. Mercedes-Benz ran service measures to replace them, and later engines use a different injector.
At what mileage does the Mercedes OM651 have injector seal leaks and seized injectors?
Typically between 100,000–250,000 km (60,000–155,000 miles), depending on use and maintenance. If the copper seal under an injector stops sealing, combustion gas escapes past it, leaves carbon and cements the injector into the head. Reused clamp bolts and wrong torque are the usual start.
At what mileage does the Mercedes OM651 have split charge-air hoses and limp mode?
Typically between 100,000–250,000 km (60,000–155,000 miles), depending on use and maintenance. Rubber charge-air hoses soften with oil vapour and heat and split; plastic pipes crack near the clamps. Hard-working vans such as the Sprinter and Vito are the most affected.
Which cars have the Mercedes OM651 engine?
Mercedes-Benz: C-Class (W204, W205) and E-Class (W212) 200 to 250 CDI/BlueTEC; GLK (X204); ML 250 BlueTEC (W166); A-, B-, CLA- and GLA-Class 180 to 220 CDI; SLK 250 CDI; Sprinter (906, 2009–2018); Vito and Viano (W639 from 2010, W447).
Mileage windows are typical workshop experience, not manufacturer data. Engines vary by version, use and maintenance; always follow the service information for the vehicle.